One of the great challenges in the health care profession is delivering drugs and other therapeutic agents to the site(s) where their activity is needed. Thus, there are many therapeutic agents whose usefulness is compromised because current methods of delivery and administration do not result in optimal presentation of the agent to the site(s) where its activity would be most beneficial.
There is a wide variety of options for administering therapeutic agents to a patient. Each route of administration poses unique challenges. These challenges include formulating the active agent in a physiologically-acceptable carrier, directing the agent to the appropriate site, delivering a concentration and amount of active agent that is effective and not toxic, and avoiding degradation of the agent such as that which occurs when an agent is administered systemically and is exposed to enzymes, the immune system and various metabolic processes.
One particularly challenging environment for delivering active ingredients is to the site of wounds, surgical sites, and other tissue openings. These sites often require the administration of active ingredients of a nature and at a concentration that is difficult, if not impossible, to achieve utilizing systemic routes such as oral and intravenous administration. Thus, direct administration of an active ingredient is often desirable yet such direct administration using previously-known techniques faces formidable challenges in terms of delivering active agents to the specific tissues and cells where the beneficial activities are most needed. In this regard, it should be noted that traditional methods of wound irrigation have not typically been combined with contemporaneous drug delivery.
In the management and treatment of a wound there are three primary objectives: (1) prevention of infection, (2) preservation and/or restoration of function, and (3) preservation and/or restoration of cosmetic appearance. The most important of these objectives is the prevention of infection. Success in the prevention of infection directly affects the healing process and the degree to which function and cosmetic appearance can be preserved and/or restored. However, heretofore, wound irrigation has not been directly combined with the administration of drugs that can reduce infection or otherwise promote healing.
It is known that the number of bacteria is a critical determinant of whether a wound becomes infected. Experimental evidence suggests that a critical level of bacteria is approximately 105 organisms per gram of tissue. Below this level, wounds typically heal; at levels greater than 105 bacteria per gram of tissue, wounds often become infected. All traumatic wounds are contaminated by the time the wound is presented to a medical care facility for treatment (Dire, Daniel I. [1990] “A comparison of Wound Irrigation Solutions Used in the Emergency Department,” Annals of Emergency Medicine 19(6):704-708). Dirty wounds, or those that have not been treated within six hours, are likely to be contaminated with bacteria at levels that are higher than the critical level. Reducing the number of bacteria in and around the wound is critical for avoiding infection and expediting wound healing.
Methicillin-resistant Staphylococcus aureus (MRSA) infection is caused by Staphylococcus aureus bacteria—often called “staph.” Decades ago, strains of staph emerged in hospitals that were resistant to the broad-spectrum antibiotics commonly used to treat them. These antibiotics include methicillin and other more common antibiotics such as oxacillin, penicillin and amoxicillin. Dubbed methicillin-resistant Staphylococcus aureus (MRSA), it was one of the first germs to be resistant to all but the most powerful drugs.
Staph bacteria are generally harmless unless they enter the body through a cut or other wound. In older adults and people who are ill or have weakened immune systems, ordinary staph infections can cause serious illness. Staph infections, including MRSA, occur most frequently among persons in hospitals and healthcare facilities, such as nursing homes and dialysis centers, who have weakened immune systems.
In the 1990s, a type of MRSA began appearing in the wider community. Today, that form of staph, known as community-associated MRSA, or CA-MRSA, is responsible for many serious skin and soft tissue infections and for a serious form of pneumonia. When not treated properly, MRSA infection can be fatal.
MRSA infections are spreading rapidly in the United States and worldwide. According to the Center for Disease Control and Prevention (CDC), the proportion of infections that are antimicrobial resistant has been growing. In 1974, MRSA infections accounted for two percent of the total number of staph infections; in 1995 it was 22%; and in 2004 it was nearly 63%. Additionally, recent research has suggested that 30-50% of the population carries MRSA colonies on their bodies all the time, helping to facilitate the spread of infection.
Although MRSA has traditionally been seen as a hospital-associated infection, there has also been an epidemic of CA-MRSA in the United States. MRSA infections in the community are usually manifested as skin infections, such as pimples and boils. These CA-MRSA infections can occur in otherwise healthy people, and commonly occur among athletes who share equipment or personal items including towels and razors. In fact, from 2000 to present, there have been several reported outbreaks of CA-MRSA affecting high school athletic teams. This epidemic among athletes is aided by the fact that MRSA grows very rapidly in warm, moist areas such as gyms and gym locker rooms. Common cuts and abrasions such as those frequently in football and baseball now pose significant threats due to the possibility of an MRSA infection.
Vancomycin is one of the few antibiotics still effective against hospital strains of MRSA infection, although the drug is no longer effective in every case. Several drugs continue to work against CA-MRSA, but CA-MRSA is a rapidly evolving bacterium, and it may be a matter of time before it, too, becomes resistant to most antibiotics.
Different procedures of wound management have been developed to help decrease the level of bacteria present in a wound, i.e., reduce the incidence of infection. The cleansing of a wound and the site surrounding the wound to remove blood clots, debris, dirt, or other foreign materials that can introduce contaminants, including pathogenic microorganisms, is critical in reducing levels of bacteria in and around the wound. There are numerous wound cleansing procedures presently used by healthcare professionals such as debridement, excision and irrigation. See, for example, Sinkinson, Craig Alan, ed. (1989) “Maximizing A Wound's Potential For Healing,” Emergency Medicine Reports 10(11): 83-89; Lammers, Richard L. (1991) “Soft Tissue Procedures: Principles of Wound Management,” in Clinical Procedures in Emergency Medicine, Roberts and Hedges, eds., 2nd Ed., W.B. Saunders Company, pp. 515-521; Cracroft, Davis (1987) “Minor Lacerations and Abrasions,” Emergency Medicine: A Comprehensive Review, Kravis and Warner, eds., 2nd cd., Aspen Publishing Co., pp. 107-110; and Mulliken, John B. (1984) “Management of Wounds,” in Energency Medicine, May ed., John Wiley & Sons, pp. 283-286.
Irrigation is the most commonly used procedure for cleansing of open contaminated wounds. Irrigation involves the application of sterile fluids to wounds to remove loose devitalized tissue, bacterial inoculum, blood clots, loose debris, and foreign bodies proximate to and within the depths of the wound. Two critical components of any effective wound irrigation method and/or device are: (1) the application of an adequate volume of sterile irrigation solution to the wound, and (2) the use of sufficient pressure applied in an effective dispersal pattern in the delivery of the solution to effectively remove contaminants. Regarding volume, the amount of irrigation solution required will depend upon the type of wound and the level of contamination. Injuries which can introduce a high amount of bacteria into a wound (such as puncture wounds and bites) may require 1 liter or more of irrigation solution.
U.S. Pat. No. 5,071,104 describes a wound irrigation apparatus and process for cleansing wounds which includes a pressure bladder, e.g., a blood pressure cuff, disposed proximate a reservoir holding a cleaning solution. The device in the '104 patent also includes a flexible tubular conduit for transmitting the solution from the reservoir to a single nozzle. The conduit and reservoir form a two-part system which is time consuming to set up, inconvenient to use, and costly.
U.S. Pat. No. 5,133,701 describes a disposable pressurized wound irrigation device which has a pressurized chamber for providing a force upon the reservoir such that a single liquid stream of cleansing solution is expelled from the device at a constant pressure. A propellant is used in evacuating the cleanser contents of the device. This invention requires a propellant and involves a relatively elaborate manufacturing and filling process which is labor intensive and requires specialized machinery. This device is also inconvenient to use and costly.
More recently, an advantageous wound irrigation system has been developed whereby a dispersed stream of irrigation fluid is easily and effectively applied to wounds. This system is described at, for example, U.S. Pat. Nos. 5,830,197 and 6,468,253 and International Patent Applications WO 00/15279 and WO 02/007799. These disclosures are incorporated herein by reference, in their entirety.
Chlorhexidine is a chemical antiseptic, and it combats both gram positive and gram negative microbes. It is bacteriostatic, hampering the growth of bacteria, and bacteriocidal, killing bacteria. It is often used as an active ingredient in mouthwash designed to kill dental plaque and other oral bacteria. Chlorhexidine also has non-dental applications, though. It is used for general skin cleansing, as a surgical scrub, and as a pre-operative skin preparation.
Chlorhexidine is typically used in the form of acetate, gluconate, or hydrochloride, either alone or in combination with other antiseptics such as cetrimide. It can be deactivated by anionic compounds, including the anionic surfactants commonly used as detergents in toothpastes and mouthwashes.